sh: fix trigger_address_error()

The function should set BL bit, but it should not clear other flags.
So, the patch uses set_bl_bit() instead of a local asm code.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>